A non-dispersive infrared absorption method is known, in which a sample gas is directly irradiated with an infrared ray from an infrared light source to measure the gas concentration of each component without dispersing the infrared ray into those of different wavenumbers. Gas analysis with a non-dispersive infrared absorption method provides quick measurement of various components contained in a gas. Thus, analysis with a non-dispersive infrared absorption method is used for various applications as an approach to directly measure components contained in a gas.
For an infrared gas analysis device used in such analysis, it is known that variation in output of a light source, a stain on a cell and window, etc., cause measurement error. To decrease measurement error, Patent Literature 1 suggests providing, in addition to a main detector in which a gas having sensitivity to the infrared absorption band of a gas to be measured is encapsulated, a compensating detector in which a gas not having sensitivity to the infrared absorption band of a gas to be measured is encapsulated. Such a device configuration provides zero-drift correction for improvement of measurement precision.
Influence of other interferential components is considered as another cause for measurement error of an infrared gas analysis device. Specifically, it is concerned that, in some sample gas compositions, the wavenumber of the infrared peak of a component contained in the sample gas overlaps with that of another component to lower the measurement precision for a component to be measured. For such a phenomenon, for example, Patent Literature 2 suggests a technique to decrease influence of a component different from a component to be measured by providing a detector for interferential components separately from a detector for a component to be measured and using a gas filter to absorb infrared rays in a specific wavenumber region.